Catheter distal tip design and method of making

ABSTRACT

A catheter comprises a catheter shaft having a distal tip, the distal tip having an inner surface and an outer surface, the inner surface having a rounded profile. The catheter may be made by rounding the inner surface of the distal tip.

BACKGROUND OF THE INVENTION

This invention relates to both intravascular and non-vascular catheterassemblies. Catheters are commonly employed in percutaneousintravascular procedures, such as percutaneous transluminal coronaryangioplasty (PTCA), for example, to open blocked vessels with as littletrauma as possible.

Catheters employed for non-vascular procedures include the cathetersemployed in the urinary tract, or those employed to examine the lowergastrointestinal tract, for example.

Several different types of catheters are utilized for intravasculartreatment including guide catheters, angioplasty catheters, dilatationballoon catheters, medical delivery devices such as stent deliverycatheters including both the self-expanding and balloon expandablevarieties, angiographic catheters, neural catheters, urinary catheters,gastrointestinal catheters, catheters for the reproductive system, heattransfer catheters, therapeutic delivery devices, thrombectomy devices,intravenous ultrasound systems, electrophysiology devices, endoscopicdevices, and so on and so forth.

In intravascular procedures, guide catheters are commonly used to aid indelivering a balloon catheter or other interventional medical devices toa treatment site in a vessel or other lumen within the body.

In a routine coronary angioplasty procedure, a guide catheter isintroduced through the aorta until the distal end of the guide catheteris engaged with the coronary ostium. Guide catheters typically have apreformed distal tip. The distal portion of the guiding catheter islocated within the ascending aorta with the distal tip of the guidingcatheter seated in the ostium. The proximal end of the guiding catheteris torqued from outside the patient to guide the distal tip of theguiding catheter into the ostium. Guide catheters typically havepreformed bends formed along their distal portion to facilitateplacement of the distal end of the guide catheter into the ostium of apatient. Guide catheters preferably have a relatively stiff main bodyportion and softer distal tip. The stiff main body portion provides theguide catheter with sufficient “pushability” and “torqueability” toallow the guide catheter to be inserted percutaneously through aperipheral artery, moved and rotated to position the distal end of thecatheter at the desired aligning angle relative to the ostium. Inaddition, a soft distal tip at the very distal end of the cathetershould be used to minimize the risk of causing trauma to a blood vesselwall while the guide catheter is being moved through the vasculature tothe ostium.

Next, the guidewire is advanced past the distal end of the guidecatheter within the lumen of the diseased vessel and manipulated acrossthe region of the stenosis. The balloon dilatation catheter is thenadvanced past the distal end of the guide catheter over the guidewireuntil the balloon is positioned across the treatment site. After theballoon is inflated to dilate the blood vessel in the region of thetreatment site, the guidewire, balloon dilatation catheter and guidecatheter can be withdrawn.

Typical commercially available intravascular balloon catheters used forangioplasty and other vascular procedures usually have an elongatedshaft with an inflatable dilatation member on a distal portion of theshaft and a fitting on the proximal end of the shaft for the delivery ofinflation fluid through an inner lumen extending through the cathetershaft to the interior of the inflatable dilatation member.

Once in position, the balloon is inflated by supplying fluid underpressure through an inflation lumen in the catheter to the balloon. Theinflation of the balloon causes stretching of the artery and pressing ofthe lesion into the artery wall, to reestablish acceptable blood flowthrough the artery There are two common types of balloon catheterscommonly referred to as “over-the-wire” (OTW) catheters and fixed wirecatheters. An over-the-wire catheter is one in which a separate guidewire lumen is provided in the catheter so that a guide wire can be usedto establish the path through the stenoses. The dilatation catheter canthen be advanced over the guide wire until the balloon on the catheteris positioned within the stenoses. There is also a modification of anOTW catheter which is referred to as a single-operator-exchange (SOE) orrapid exchange (RE) catheter. SOE catheters have a guide wire lumen thatonly extends through a portion of the catheter. The guide wire lumenextends from the distal end of the catheter to a distal porthole on thecatheter tube.

A fixed wire catheter acts as its own guide wire, and thus there is noneed for a separate guide wire lumen.

Angiographic catheters can be used in evaluating the progress ofcoronary artery disease in patients. Angiography procedures are used toview the patency of selected blood vessels. In carrying out thisprocedure, a diagnostic catheter also having a desired distal endcurvature configuration may be advanced through the vascular system ofthe patient until the distal end of the catheter is steered into theostium.

The profile of the outer surface of the distal tip of a catheter may berounded so as to result in a tip which reduces the likelihood of traumato the vessel. However, rounding the tip on the outside using currentmethods, may leave the edge of the tip on the inner lumen sharp. Whenthe catheter is advanced over the guidewire, or when the guidewire isretracted into the catheter, this sharp edge can act similar to a knife,scraping material from the guidewire, and can increase the frictionbetween the inner catheter shaft and the guidewire. If a lubriciouscoating is present, this may also be scraped off. Furthermore, having asharp tip on the inner lumen can results in parts of the tip whichactually break off from the catheter.

There remains a need in the art for a catheter having an inner distaltip which has a smoother, more rounded profile.

SUMMARY OF THE INVENTION

The present invention, in one embodiment, relates to a catheter assemblyhaving a distal tip having an inner and an outer surface, wherein atleast the inner surface has a longitudinal cross-sectional profile viewof the distal tip wherein the inner surface curves toward the outersurface at the distal end, and desirably both the inner and the outersurface have a curved profile.

In one embodiment, the curve has a radial arc.

The rounded or curved profile may be formed using any technique known inthe art. In some embodiments, laser energy is employed. As used herein,the term “rounded” or “rounding” shall hereinafter refer to curvature ina region or to providing curvature to a region.

Lasers suitable for use herein are those which generate energy having awavelength of about 450 nm or less, suitably about 350 nm or less, moresuitably 250 nm or less and even more suitably about 200 nm or less.Excimer lasers are suitable for use herein and are capable of generatingenergy in the UV range at wavelengths of about 450 nm or less. Forexample, the argon-fluoride (ArF) excimer laser produces UV radiationhaving a wavelength of 193 nm and the fluorine (F2) laser produces UVradiation having a wavelength of 157 nm. An example of one type of laserwhich is suitable for use herein is an excimer laser. One example of anexcimer laser which produces UV radiation having a wavelength of over200 nm is krypton-fluoride (KrF) excimer laser which produces UVradiation having a wavelength of 248 nm.

Excimer lasers are advantageous because they produce a very highlyuniform beam, i.e. uniformity of intensity across the beam diameter. Thepresent invention also relates to a method of producing a catheterhaving a distal tip having an inner surface and an outer surface,wherein the inner surface is formed by applying a laser beam to at leastthe inner surface of the distal tip.

The resultant distal tip has an inner surface having a rounded profile.Desirably, the laser beam is applied to the outer surface as well,resulting in the outer surface of the distal tip having a roundedprofile as well.

Providing a catheter having a distal tip with a curved profile reducesthe likelihood of scraping by the inner surface of the distal tip on aguide wire being advanced therethrough, and reduces the likelihood oftrauma to the vessel produced by the tip because rounding the innersurface reduces the sharpness of the inner edge as well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective side view of a balloon catheter assembly inaccordance with the invention.

FIG. 2 is cross-sectional view of the distal end of balloon catheterassembly as shown in FIG. 1.

FIG. 3 is a diagrammatic longitudinal cross-sectional partial view of atraditional distal tip for a catheter shaft.

FIG. 4 is a partial side view of a traditional distal tip of a ballooncatheter assembly according to the invention.

FIG. 5 is a partial perspective view of a distal tip of a ballooncatheter assembly according to the invention.

FIG. 6 is a diagrammatic longitudinal cross-sectional partial view of adistal tip for a catheter assembly according to the invention.

FIG. 7 is a fluence profile which may be employed for forming a distaltip by laser ablation according to the invention.

DETAILED DESCRIPTIONS OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein by way of illustration, specific embodimentsof the invention. This description is an exemplification of theprinciples of the invention and is not intended to limit the inventionto the particular embodiments illustrated.

Any US patents and applications, and all other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

In one embodiment, the present invention relates to a catheter having adistal tip, the distal tip having an inner surface and an outer surface,and in a longitudinal cross-sectional profile view of the distal tip,the inner surface curves towards the outer surface at the distal end. Inone embodiment, the curve has a radial arc.

The outer surface may also have a curved profile wherein it curvesinward toward the inner surface at the distal tip, or the outer surfacemay have a profile which remains substantially the same from theproximal end of the distal tip to the distal end of the distal tip.

Rounding or curving of the inner and/or the outer surface, can result ina tip which is less traumatic to a vessel during use. The roundedprofile of the inner surface of the distal tip can decrease the amountof friction during contact with a second surface such as a guide wire,for example.

In the case of an angioplasty balloon catheter, rounding of the innersurface can result in a smoother surface, reducing the likelihood ofscraping material from the guide wire, or scraping catheter lubricantfrom both.

Further, the use of softer polymeric materials in combination with acurved inner surface profile may further reduce the likelihood ofbreakage or tearing of the catheter tip which can occur with a sharp,non-rounded inner profile.

Turning now to the figures, represented generally at 25 in FIG. 1, is arepresentative OTW angioplasty balloon catheter according to theinvention. Such balloon catheters are discussed, for example, incommonly assigned U.S. Pat. Nos. 6,113,579, 6,517,515, 6,514,228, eachof which is incorporated by reference herein in its entirety. In thisembodiment, catheter 25 has an elongate shaft assembly 50 and a balloonassembly 52. A conventional OTW-type manifold assembly 54 is connectedto proximal end of shaft assembly 50. The shaft assembly 50 includes aninner tube 56 and an outer tube 58. Outer tube 58 is coaxially disposedabout inner tube 56 to define an annular inflation lumen 60. In thisembodiment, distal tip 10 of inner tube 56 has a curved inner profilewhich when viewed in a longitudinal cross-sectional view, shows acurvature from the inner surface to the outer surface at the distal end18 of the distal tip 10, according to the invention. Manifold assembly54, is further shown with a strain relief 62.

FIG. 2 is a cross-sectional view of the distal end of the catheterassembly showing balloon 52 over inner tube 56 having distal tip 10according to the invention. Distal tip 10 of balloon 52 may be formedhaving a smooth, rounded inner profile (not shown). Distal tip 10 may beformed from the same material or from a different material than that ofballoon 52. Distal tip 10 may comprise a soft material that minimizestrauma to the surrounding tissue as catheter 25 is advanced to its finaldestination within the vasculature. Additionally, the rounding of thetip on the outer surface as well as on the inner surface, furtherreduces the likelihood of trauma to surrounding tissue.

This description of a balloon catheter is intended for illustrativepurposes only, and not as a limitation on the scope of the presentinvention. There are variations in the design of such devices known tothose of skill in the art.

The distal tip design according to the invention offers a rounded,softer tip design which may result in less trauma to the vessels throughwhich the catheter assembly is delivered. FIG. 3, in contrast, is arepresentative diagrammatic longitudinal cross sectional partial view ofa traditional distal tip 10 for a catheter assembly. Distal tip 10 has aproximal end 16 and a distal end 18 and a curved outer surface 20 but asharp inner surface 30 at the distal tip in the region where the tipopening is located.

FIG. 4 is a partial side view of a simple OTW balloon catheter 25 beingadvanced from the proximal end (not shown) over a guide wire 40. As canbe seen from FIG. 3, the inner surface 30 of the distal tip 10 ofballoon catheter 25 is sharp in the traditional sense. If the guide wire40 is provided with a lubricious coating, for example, this sharp edge30 may cause scraping of the lubricious coating from the surface of theguide wire 40.

FIG. 5 is a perspective partial view of the distal tip 10 of an OTWcatheter shown in combination with a guide wire 40. In this embodiment,the inner profile has been rounded, reducing the sharp inner edge 30 asshown in FIGS. 1 and 2.

FIG. 6 is a diagrammatic representation of a longitudinal cross sectionof the distal tip 10 shown as a partial view. In this embodiment, distaltip 10 has a proximal end 16 and a distal end 18 and is shown havingboth a curved outer profile 30 and in a longitudinal cross-sectionalprofile view of the distal tip, an inner surface 20 which curves towardthe outer surface at the distal tip, reducing the sharpness of edge 22shown in FIGS. 1 and 2 which may also reduce the likelihood of trauma toa patient's vessel, as well as reducing the likelihood of scraping ofthe guide wire surface. Furthermore, scraping, as discussed above, mayhave a negative impact on a lubricious coating such as on a guide wire,or on the catheter surface itself. As can be seen in FIG. 4, thecircumference of the inner surface increases slightly from the proximalend 16 to the distal end 18 of the inner surface. The circumference ofthe outer surface may decrease slightly from the proximal end 16 to thedistal end 18 of the distal tip, or the circumference of the outersurface may remain substantially unchanged as well.

The smoother, rounded inner edge, also reduces the likelihood of ascraping effect on any adjacent surface with which the distal tip maycome in slidable contact. In this embodiment, the curvature of the outersurface is shown substantially equal to and opposite the curvature ofthe inner surface, or in other words, the curvature of the outer surfaceis substantially a mirror image of the inner surface.

The shape of the catheter inner and/or outer surface, shall not beintended to be limited to those which are purely circular. Othergeometries are contemplated herein. For example, the shape could beelliptical as well.

Distal tip 10 may be formed from the same material, or from a differentmaterial than the catheter shaft. Any suitable polymeric material may beemployed herein and include both elastomers and non-elastomericpolymers.

Suitable materials may include, but are not limited to, polyolefinsincluding polyethylene, polyamides including nylon and copolymers suchas poly(ether-block amide), polyimides, polyurethanes, polyestersincluding the PET (polyethylene terephthalate) and PBT (polybutyleneterephthalate) copolymers and elastomeric polyesters such aspoly(ether-block-ester), latex, silicones, rubbery block copolymers suchas styrenic block copolymers including SEBS(styrene-ethylene/butylenes-styrene), SIS (styrene-isoprene-styrene),SBS (styrene-butadiene-styrene), SEPS(Styrene-ethylene/propylene-styrene), butylene and isobutylene rubber,and so forth, any copolymers thereof, and mixtures thereof. As usedherein, the term “copolymer” shall be used to refer to any polymerformed from two, three or more monomers. Some of the above classes ofmaterials such as the polyesters, for example, include both elastomericand non-elastomeric polymers in the class. The above list is notexhaustive, and is not intended to limit the scope of the presentinvention. Many suitable polymeric materials not listed here, are knownto those of skill in the art.

In some embodiments, the material of the distal tip may be formed from amaterial which is softer than that of the shaft. Typically, theseproperties are measured using a Shore Durometer scale. The ShoreDurometer hardness of the distal tip in these embodiments may be lessthan the Shore Durometer of the catheter shaft, or of at least a portionof the shaft.

Other embodiments, as in the case of a chronic total occlusion (CTO)device, the distal tip may be formed from a material which is not softerthan that of the catheter shaft.

In one embodiment, the rounded inner edge may be formed using laserablation techniques. However, any known techniques, such as abrasion forexample, of rounding the inner edge and/or outer edge may be employed.

Lasers may be employed in rounding the inner and/or outer edge of thedistal tip. Suitable lasers which may be employed include thoseproducing energy at a wavelength of about 450 nm or less.

One example of a laser employed is an excimer laser. Excimer lasers arepulsed gas discharge lasers which produce wavelength output in theultraviolet region of the spectrum. The wavelength output depends uponthe active gas fill of the laser. For example, the argon-fluoride (ArF)excimer laser produces UV radiation having a wavelength of 193 nm andthe fluorine (F2) laser produces UV radiation having a wavelength of 157nm. One example of an excimer laser which produces UV radiation having awavelength of over 200 nm is krypton-fluoride (KrF) excimer laser whichproduces UV radiation having a wavelength of 248 nm. Xenon-chlorideexcimer lasers produce UV radiation having a wavelength of 308 nm andxenon-fluoride excimer lasers produce UV radiation having a wavelengthof 351 nm.

In one embodiment, the laser employed is the ArF excimer lasergenerating UV radiation at a wavelength of 193 nm.

In another embodiment, the laser employed is the F2 excimer laser whichgenerates UV radiation at a wavelength of 157 mm.

Excimer lasers are advantageous because they produce a very short pulselength which allows the materials to be ablated rather than melted. Atypical Excimer laser has a pulse length of the order of nanoseconds.Femtosecond lasers may also be advantageously employed in the presentinvention.

Excimer lasers also produce a very highly uniform beam, i.e. uniformityof intensity across the beam diameter.

The lower the wavelength employed, the higher the absorption by thepolymer which makes ablating at the lower wavelengths of about 250 nm orless, much more precise than the higher wavelengths.

The process of laser ablation involves directing a laser at a desiredlocation of the distal tip and ablating the material in the desiredpattern on the inner and/or outer surface of the distal tip.

The process of laser ablation has a threshold fluence. Fluence is alevel of required energy density, and is a measurement of the projectedlaser pulse energy per unit area per pulse on the substrate, which maybe varied by either changing the laser pulse energy, or by changing theablation area. At fluences below a certain threshold, Fth, onlyminuscule etching (<0.05 μm per laser pulse) is observed. Thus, it isnecessary to maintain the laser fluence above the threshold. When laserfluence is above the threshold, the etch depth, d, per pulse increasesrapidly with increasing fluence. At a fluence just above the threshold,the etch depth, d, per pulse varies logarithmically with the fluence, F:d=ln(F/Fth)

With the increase of fluence, the relationship between etch depth andfluence changes from logarithmic to approximately linear. UV laserablation of polymers is described in, for example in an article by Y. V.Afanasiev et al., Hydrodynamic regimes of UV laser ablation of polymers,Applied Physics, A64, 561-572 (1997) which is incorporated by referenceherein in its entirety.

One way in which to create the rounded tip both on the inner and theouter surface of the distal tip, is to direct the laser beam along theaxial direction and provide a fluence profile as shown in FIG. 5.

In FIG. 7, half of the tubular member is represented as can be seen fromthe location of the inner lumen axis 50. In the case of a round tube,the required fluence profile may be obtained by forming an annular beamprofile with an energy profile which is parabolic in a radial directionwith a minimum density level just above the threshold fluence in betweenthe inner and outer radius of the annulus. The annular shape isprojected by means of lenses on the tip of the catheter such that theouter circumference of the annular shape is projected on the outercircumference of the tube and the inner circumference of the annulus onthe inner circumference of the tube. FIG. 3 illustrates, in part, thatthe extent of the rounding and the resulting profile of the tip will bea function of the number of pulses. Thus, after 50 pulses, shown atcurve 42, the curvature will be greater than after 10 pulses, shown atcurve 44.

The method according to the invention may be employed in the formationof a distal tip for a catheter shaft employed in any type of catheterassembly used in intravascular procedures as well as non-vascularprocedures including, but not limited to, guide catheters, balloonangioplasty catheters, i.e. dilatation catheters, SOE or RE catheters,OTW catheters, fixed wire catheters, medical device delivery cathetersincluding the stent delivery devices in both the self-expanding andballoon expandable varieties, therapeutic substance delivery devices,thrombectomy devices, endoscopic devices, angiographic catheters, neurocatheters, dilitation catheters, urinary tract catheters,gastrointestinal catheter devices, heat transfer catheters includingthermal catheters and cooling, intravascular ultrasound systems,electrophysiology devices, and so on and so forth.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the attached claims. Thosefamiliar with the art may recognize other equivalents to the specificembodiments described herein which equivalents are also intended to beencompassed by the claims attached hereto.

1. A catheter comprising: a catheter shaft and a distal tip, the distaltip having a proximal end and a distal end, the distal tip having aninner surface and an outer surface, and in a longitudinalcross-sectional profile view of the distal tip, the inner surface curvestowards the outer surface at the distal end and is substantiallystraight proximal the distal end, and the outer surface curves towardthe inner surface or the outer surface remains substantially unchangedat the distal end and is substantially straight proximal the distal end.2. (canceled)
 3. The catheter of claim 1, the inner surface having afirst circumference at the distal tip and a second circumferenceproximal the distal tip, wherein the first circumference at the distaltip is at least 10% larger than the second circumference proximal thedistal tip.
 4. The catheter of claim 1 wherein the distal tip is formedfrom at least one member selected from the group consisting ofpolyolefins, polyamides, polyurethanes, polyimides, polyesters,silicones, rubbery block copolymers, latex, copolymers thereof andmixtures thereof.
 5. The catheter of claim 1 wherein the distal tip isformed from a block copolymer.
 6. The catheter of claim 1 wherein saiddistal tip is formed of a polymeric material which is softer than saidpolymeric material from which said catheter shaft is formed as measuredby a Shore Durometer scale.
 7. The catheter of claim 1 wherein saiddistal tip is formed from a polymeric material which has a hardnesswhich is equal to or greater than the polymeric material from which thecatheter shaft is formed as measured by a Shore Durometer scale.
 8. Thecatheter of claim 1 wherein the curvature of the outer surfacesubstantially mirrors the curvature of the inner surface.
 9. A method ofmanufacturing a catheter shaft having a distal tip, the distal tiphaving an inner surface and an outer surface, the method comprising thesteps of: providing said catheter shaft and said distal tip; androunding the inner surface of the distal tip such that the circumferenceof the inner surface increases in a longitudinal direction toward thedistal tip.
 10. The method of claim 9 further comprising the step ofrounding the outer surface of the distal tip.
 11. The method of claim 9wherein the rounding step comprises laser ablation of material from thesurface.
 12. The method of claim 11 wherein said laser is an ultravioletlaser.
 13. The method of claim 11 wherein said laser produces UVradiation having a wavelength of about 450 nm or less.
 14. The method ofclaim 11 wherein said laser produces UV radiation having a wavelength ofabout 351 nm or less.
 15. The method of claim 9 wherein the distal tipis integral with said catheter shaft.
 16. The method of claim 9 whereinthe distal tip is formed separately from said catheter shaft and themethod further comprises the steps of disposing the distal tip on thecatheter shaft.
 17. The catheter of claim 5 wherein said block copolymerhas styrene end-blocks and diene mid-blocks.